Primary shoots bullets with huge force, secondary throws chairs.this was made in 5 minutes with Pyromaniac1444's Swep Generatorit spams an LUA error when shot for some unknown reason, it doesn't do anything so just ignore it

This download looks like an addon. You need to extract the downloaded zip and put the addon folder in your Garry's Mod addons folder. You should end up with a directory structure similar to below: